1. Field of the Invention
This invention relates to a heat-resisting steel having excellent strength and corrosion resistance, and more particularly to a heat-resisting steel having improved properties as a valve material for use in valve component parts of an internal combustion engine.
2. Description of the Prior Art
Heretofore, heat-resisting steels such as SUH 1, SUH 3, SUH 11 and the like have largely been used in an intake valve for an internal combustion engine such as gasoline engine, diesel engine or the like. Lately, it is required to use materials having excellent high-temperature strength and oxidation resistance as a valve material with the increase of compression ratio in the engine (or the use of turbo or diesel engine), and these materials are required to have a cold forging property in view of the improvement of productivity. However, the aforementiond SUH series steels are still insufficient to satisfy the above requirements. Further, all of these steels contain 8 to 12% of chromium, while chromium producing district is restricted considerably, so that there is a great fear on the acquisition of chromium.